Astronomy

Big Bang Theory

The leading scientific explanation for how our universe began, expanding from a hot, dense point about $13.8$ billion years ago.

Cosmic Microwave Background (CMB)

Faint, cool glow of leftover heat from the Big Bang, detectable in every direction in the universe.

Galactic Redshift

The phenomenon where light from distant galaxies is stretched, indicating that the universe is still expanding.

Doppler Effect

The apparent change in pitch or frequency of a wave when the source and listener move relative to each other.

Blueshift

The phenomenon where light waves get compressed to shorter wavelengths when an object moves toward Earth.

Redshift

The phenomenon where light waves get stretched to longer wavelengths when an object moves away from Earth.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

Nuclear Fission

The splitting of a heavy atomic nucleus, such as Uranium-235, releasing energy and additional neutrons.

Star Lifecycle

The stages a star goes through from formation in a nebula to becoming a white dwarf, neutron star, or black hole.

Kepler's First Law

Planetary orbits are ellipses with the Sun at one focus.

Kepler's Second Law

A planet sweeps out equal orbital areas in equal times, moving faster when closer to the Sun.

Kepler's Third Law

The square of a planet's orbital period is proportional to the cube of its average distance from the sun: $T^2 \text{ is proportional to } a^3$.

Newton's First Law

An object remains at rest or in uniform motion unless acted upon by a net external force.

Newton's Second Law

The force on an object equals mass times acceleration: $F = ma$.

Newton's Third Law

For every action, there is an equal and opposite reaction.

Newton's Law of Universal Gravitation

Every object with mass attracts every other object with mass: $F = G \frac{m_1 m_2}{r^2}$.